Hi there I have a MacBook 2009 edition which only has 4GB of memory, 2 of which I allow for Windows 7 when running VMWare Fusion 4. It also has about 15-19GB of disc space free. Earlier this week I suspended my virtual Windows 7. I then plugged in 2 firewire hard drives. I then let CarbonCopyCloner clone my internal hard drive and Time Machine run it's back up. The next morning I got up and all was well, the jobs having been done. In fact I repeated the process a couple of nights later and again all was well. Great. Just how I like it. However when I did the exact same steps under Lion, it would cause my computer to effectively crash. It wouldn't be able to find the external hard drives and other things might occur but these only happened after I had run VMWare Fusion. I would have to restart the computer. This might often mean a backup being delayed as I may not want to restart my computer. May be VMWare fixed a bug in Fusion but the impression I get from reading posts in the past when I was experiencing the problems, was that it were Mac OS related bugs. I've yet to try Time Machine whilst VMWare Fusion 4 is running but I am confident it would just work. Moral of the story, if your stil on Lion and your Mac can support Mountain Lion, upgrade. Lion must be Apple's version of Windows Vista. Unlike Microsoft though, they upgraded quicker. I only upgraded to Lion because I wanted to use iCloud. Now I can use iCloud and an OS which works better! If you have any other examples of where Mountain Lion fixes a problem that Lion had, post them here.